Is Fracking for Enhanced Geothermal Systems the Same as Fracking for Natural Gas?

Meg Cichon

Advocates for both natural gas and geothermal are up in arms
over whether fracking for enhanced geothermal systems should be
scrutinized with the same parameters as natural gas.

Ormat sucessfully used EGS technology to increase the
capacity of its Desert Peak 2 plant in Nevada by 1.2MW.
Photo Source: Ormat

The U.S. geothermal industry recently scored a big win when its
first enhanced geothermal system (EGS) project went online in April.
ORMAT (NYSE:ORA)
was able to stimulate a previously unproductive well at its Desert
Peak project with EGS technology — injecting fluid into a well to
reopen cracks and create a resource reservoir — and found an
additional 1.2 megawatts (MW) of capacity. Renewable energy experts
applauded the project, dubbing it a "game-changer" and a "shining
moment" for the industry.

Though the project represents a breakthrough for EGS
technology and the geothermal industry in general, EGS has
come under fire, with opponents accusing it as being just as
dangerous as oil or natural gas hydraulic stimulation, commonly
known as fracking. While traditional geothermal energy is viewed as
clean renewable energy, could EGS technology, with its similar
"fracking methodology," coupled with its rocky past, come under the
same intensive scrutiny as natural gas fracking?

EGS and Earthquakes

Perhaps the most notorious EGS project is one that was never
completed in Basel, Switzerland — constructed on a known
seismic fault and suspended in 2006 when it generated earthquakes
that reportedly caused millions of euros in damage to local
infrastructure. The project was cancelled in 2009 after several
reports said that if continued, it would cause more earthquakes
and would lead to more damage each year.

"It's easy to generate a lot of fear. You can scare people about
things without providing much solid information," said David
Stowe, communications director at AltaRock. "The Basel story is
dredged up over and over again — but we have learned from it,
and it is pretty easy to put safeguards in place that will
severely minimize risk."

Since its cancelation, many have pointed to the Basel project as
a reason to avoid EGS altogether. However, the U.S. Department of
Energy (DOE) remained undeterred, and developed geothermal-induced seismicity protocol and further
stringent safety measures with Lawrence Berkley National Labs to
prevent major seismic events - the only protocol in place for any
sub-surface energy industry, according to Doug Hollet, director of
the DOE geothermal energy program.

The DOE has been working on several EGS projects, including
AltaRock's innovative Newberry project in Bend, Oregon. To ensure
that the Newberry project does not cause significant seismic
events, AltaRock has implemented rigorous protocols and created an
advanced microseismic network system of about 20 seismometers that
surrounds the project both on the surface and in wells 1,000 feet
below the earth. The seismometers pick up the sounds that
fractures make when they grow, triangulate and then displays the
location of the fracture zone on a computer screen — AltaRock
has its own modeling software for this, said Stowe.

In natural gas, seismic activity is not the major concern when it
comes to the fracking process. According to Stowe, the reinjection
of the spent working fluid causes the most problems. "It creates a
huge bulge when you re-inject all this water; pressure builds and
the earth moves to compensate for that, which can cause a seismic
event," said Stowe — adding, however, that this isn't a
common occurrence.

According to Andrew Place, interim director and president of the
Center for Sustainable Shale Development, seismicity is more of a
concern for EGS due to the ongoing nature of the technology,
whereas natural gas enters a site, fracks for the resource and
moves on. "[For natural gas] the strong concern is for disposal
wells, and if you don't site them carefully and drill in a close
proximity to an existing fault that is highly stressed, you could
set off a substantial seismic event," he said. This can be avoided
with pre-drill modeling to ensure the avoidance of fracture
networks and monitoring for seismic events — similar to the
precautions already being taken at the Newberry project site.

Fracking vs Slipping

According to Hollett, the fundamental difference between natural
gas fracking and EGS fracking is the injection process. The oil
and gas industry injects water and a proppant (a mix of sand and
chemicals), at a very high pressure of around 9,000 psi or more,
which breaks though the rock and holds the cracks open; otherwise
they would close when the fluid stops flowing.

EGS, however, uses water, and sometimes acid, to shear the rock
and cause a "slip." "You're trying to make two rock faces slide
past each other slightly, which creates a little bit more space
between them," said Lauren Boyd, EGS program manager at the DOE.
This is where fractures or weaknesses in the rock likely existed
already and were plugged by mineral deposits over time. Boyd
compared the process to putting an ice cube in a glass of hot
liquid: "cracks will form where there are existing deformities in
the ice, which is similar to what happens in the subsurface with
closed fractures," she said.

As for long-term effects, "we are talking about very small
fractures very deep in the earth — there is really little or
negligible long-term impact there," said Hollett.

Contamination Concerns

Since many believe EGS technology to be similar to natural gas
fracking, the same concerns about leakage, spills and resulting
groundwater and soil contamination exist for both technologies.
After all, according to Popular Mechanics, in the past two years
alone, natural gas fracking has caused numerous surface spills
including several projects that have contaminated groundwater.

AltaRock plans to combat these problems at the Newberry project
by using a multizone stimulation process. Water is injected into a
single well at a pressure of about 2,000 psi to stimulate cracks
in the rock, which eventually spider out to create a "zone." Once
a zone is complete, pressure is dropped to 1,000 psi and a
diverter made of biodegradable plastic (similar to plastic
developed that allows water bottles to biodegrade in landfills) is
injected into the well to "gum up" the cracks, according to Stowe.
Pressure is then increased to 2,000 psi to start a new fracture
zone, and then a new batch of diverter is made to plug up holes at
hotter temperatures. The process repeats until all zones are
created, and water flow is then stopped to allow the well to heat
up. It takes about one week for the diverter to break down into
water and CO2, which is eventually used to generate
power once the plant is built, said Stowe.

According to several experts, many of the issues related to
natural gas fracking can be prevented with the same type of proper
protocol and procedures in use at the Newberry project. For
example, in 2011 Chesapeake Energy (CHK) reportedly lost control
of a well in Pennsylvania. The well cracked, spilled and
contaminated a nearby stream - this could have been prevented by
using stronger cement and casings to ensure an impermeable seal.

The natural gas industry is slowly realizing that it needs to
reduce these issues to gain public confidence, said Stowe, so it
is working with state regulators to create some of the same
regulations that exist for geothermal. Texas became the first
state to require companies to reveal what is in its fracking
solutions. And more recently, Illinois passed some of the "toughest
fracking regulations" in the U.S., and will require companies to
reveal chemicals used and test groundwater before and after
fracking. "The best way to get around issues is to adequately fund
state agencies, employ smart people with decades of experience,
gain support from the surrounding regulatory framework and a
commitment from the Environmental Protection Agency," said Place.

Though there are far fewer EGS projects compared to the thousands
in natural gas, Hollett is confident that if the geothermal sector
follows best practices, drills wells properly and works with
regulatory agencies, it will mitigate the potential for any
adverse environmental impacts.

Place agrees, and points out that both technologies have
potential risks, neither of which are served well by avoiding
them. Though there are different risk pathways, he said, risks are
risks, and the industries not only needs strong regulations, but
strong practices and responsible development — it "goes
hand-in-hand" for both technologies.

"At Newberry [regulations are] rigorous - that's how it should
be, and that's okay. Fracking should be completely safe, and if it
isn't then someone is doing a sloppy job," said Stowe. "I'm
hopeful that the natural gas industry will [work to create
regulations and protocols], because in my opinion fracking is here
to stay — I don't see it going anywhere any time soon."

Meg Cichon is an Associate Editor at RenewableEnergyWorld.com,
where she coordinates and edits feature stories, contributed
articles, news stories, opinion pieces and blogs. She also
researches and writes content for RenewableEnergyWorld.com and REW
magazine, and manages REW.com social media. Formerly, she
was an Associate Editor of ideaLaunch in Boston, MA. She holds a
BA in English from the University of Massachusetts and a
certificate in Professional Communications: Writing from Emerson
College.

This article was first
published on RenewableEnergyWorld.com, and is republished
with permission.